1. Field of Invention
The invention is in the field of organic chemistry. The invention relates to a process that converts a mixture of dehydration products of (3R,3′R,6′R)-lutein, hereto after referred to as anhydroluteins, to a mixture of (3R)-β-cryptoxanthin and (3R,6′R)-α-cryptoxanthin by catalytic hydrogenation with a variety of heterogeneous and homogeneous catalysts under mild conditions at atmospheric pressure. Two alternative processes have also been developed that can convert unesterified lutein to anhydroluteins. The invention also relates to a process that converts other lutein sources to anhydroluteins.
2. Background of the Art
β-Cryptoxanthin, as measured through blood plasma samples, is associated with blood pressure reduction as seen in an Oxford University large intervention trial (John J H, Ziebland S, Yudkin P, Roe L S, Neil H A. Effects of fruit and vegetable consumption on plasma antioxidant concentrations and blood pressure: a randomised controlled trial. Lancet 2002; 359(9322):1969-74). Healthy and diseased subjects have been studied in a variety of prospective trials to correlate β-cryptoxanthin levels with cardiovascular parameters (John et al.; Appel L, Moore T, Obarzanek E, et al. A clinical trial of the effects of dietary patterns on blood pressure. N Engl J Med 1997; 336(16):1117-24). There seems to be a relationship with cardiovascular markers such as LDL oxidation (Roberts W G, Gordon M H, Walker A F. Effects of enhanced consumption of fruit and vegetables on plasma antioxidant status and oxidative resistance of LDL in smokers supplemented with fish oil. Eur J Clin Nutr 2003; 57:1303-10), DNA synthesis (aortic cells) (Carpenter K L, Hardwick S J, Albarani V, Mitchinson M J. Carotenoids inhibit DNA synthesis in human aortic smooth muscle cells. FEBS Lett 1999; 447(1):17-20), malondialdehyde, and myocardial infarction onset. Subjects with either coronary artery disease (CAD), congestive heart failure (CHF), coronary heart disease (CHD), angina pectoris, or myocardial infarction onset have all shown to have lower β-cryptoxanthin levels with respect to healthy age-matched subjects (Meraji S, Abuja P M, Hayn M, et al. Relationship between classic risk factors, plasma antioxidants and indicators of oxidant stress in angina pectoris (AP) in Tehran. Atherosclerosis 2000; 150(2):403-12; Morris D, Kritchevsky S, Davis C. Serum carotenoids and coronary heart disease: the Lipid Research Clinics Coronary Primary Prevention Trial and Follow-up Study. JAMA 1994; 272:1439-41; Ruiz Rejon F, Martin-Pena G, Granado F, Ruiz-Galiana J, Blanco I, Olmedilla B. Plasma status of retinol, alpha- and gamma-tocopherols, and main carotenoids to first myocardial infarction: case control and follow-up study. Nutrition 2002; 18(1):26-31; Dwyer J H, Paul-Labrador M J, Fan J, Shircore A M, Bairey Merz C N, Dwyer K M. Progression of Carotid Intima-Media Thickness and Plasma Antioxidants: The Los Angeles Atherosclerosis Study. Arterioscler Thromb Vasc Biol 2004; 24:313-19; Vogel S, Contois J H, Tucker K L, Wilson P W, Schaefer E J, Lammi-Keefe C J. Plasma retinol and plasma and lipoprotein tocopherol and carotenoid concentrations in healthy elderly participants of the Framingham Heart Study. Am J Clin Nutr 1997; 66(4):950-8). Inflammatory markers such as C-reactive protein and fibrinogen have also been linked to low β-cryptoxanthin levels (Kritchevsky S B, Bush A J, Pahor M, Gross M D. Serum carotenoids and markers of inflammation in nonsmokers. Am J Epidemiol 2000; 152(11):1065-71). Inflammation and the relationship to heart disease is a relatively new area of study. Currently, there are no products available for the dietary supplement market which have appreciable levels of β-cryptoxanthin in them or contain β-cryptoxanthin as the major ingredient.
There have also been some preliminary studies looking at the effect of beta cryptoxanthin on bone growth and the inhibition of bone reabsorption. In vitro studies have shown a positive effect of β-cryptoxanthin increasing bone calcium and enhancing bone alkaline phosphatase (Yamaguchi, M, Uchiyama, S. Effect of carotenoid on calcium content and alkaline phosphatase activity in rat femoral tissues in vitro: the unique anabolic effect of beta-cryptoxanthin Biol. Pharm. Bull 2003; 26(8): 1188-91) (Uchiyama, A, Yamaguchi, M. Inhibitory effect of beta cryptoxanthin on osteoclast-like cell formation in mouse marrow cultures. Biochem. Pharmacol. 2004; 67: 1297-13-5). Oral studies in rats have shown similar results. (Uchiyama, S, Sumida, T, Yamaguchi, M. Oral administration of beta-cryptoxanthin induces effects on bone components in the femoral tissues of rats in vivo. Biol. Pharm. Bull. 2004; 27(2): 232-5. A PCT was filed on these findings (Yamaguchi, M. Osteogenesis promoter containing β-cryptoxanthin as the active ingredient PCT WO 2004/037236 A1).
This invention is an improvement to the process described in PCT/US2001/23422 (which is incorporated herein by this reference) that converts commercially available (3R,3′R,6′R)-lutein containing 5% (3R,3′R)-zeaxanthin in two steps to a mixture of (3R)-β-cryptoxanthin and (3R,6′R)-α-cryptoxanthin. In the first step according to PCT/US2001/23422, (3R,3′R,6′R)-lutein is allowed to react with an alcohol, used as solvent, in the presence of catalytic amount of an acid between 45-50° C. to give the corresponding 3′-alkyl ethers of lutein. Water and additional acid is then added to the mixture and the temperature is raised to 78-88° C. to convert the resulting lutein 3′-alkyl ethers to a mixture of anhydroluteins I, II, and III, quantitatively (Scheme 1 of FIG. 1). At the beginning of this transformation, anhydrolutein I is the major product and anhydrolutein II and III are the minor products. As heating continues at 78-88° C., anhydroluteins I and II are partially isomerized to anhydrolutein III within 7-20 h depending on the nature of the alcohol. In the second step of the PCT/US2001/23422, the resulting product, rich in anhydrolutein III is allowed to react with about 1.3 equivalent of a hydride donor and about 3.5-4 equivalent of a strong organic acid in a chlorinated solvent at ambient temperature for about 1-5 hours to give a mixture of E/Z-(3R)-3-cryptoxanthin, E/Z-(3R,6′R)-α-cryptoxanthin, and minor quantities of unreacted anhydroluteins I and II, as well as recovered E/Z-(3R,3′R)-zeaxanthin.
The present invention provides an alternative route to the second step of PCT/US2001/23422 for making (3R)-β-eryptoxanthin and (3R,6′R)-α-cryptoxanthin from anhydroluteins and eliminates the use of chlorinated solvents and reagents such as trifluoroacetic acid, and borane-amine complex. This is accomplished by heterogeneous or homogeneous catalytic hydrogenation of anhydroluteins according to the scheme illustrated in FIG. 1.
In addition, the present invention improves the first step of transformation of (3R,3′R,6′R)-lutein to anhydroluteins to reduce the amounts of solvents used as well as increasing the purity and stability of the products.
While in all of the above processes, unesterified lutein has been employed as the starting material, the present invention has further developed two alternative processes that can employ a mixture of esterified luteins as the starting material to prepare anhydroluteins that can then be transformed to (3R)-β-cryptoxanthin and (3R,6′R)-α-cryptoxanthin by catalytic hydrogenation.